如何使用玩笑测试redux-saga的所有效果

问题描述

function* mySaga() {
  const [customers, products] = yield all([
    call(fetchCustomers),
    call(fetchProducts)
  ])
}

我想测试一下所有效果，但得到:Invalid attempt to destructure non-iterable instance

I want to test all effect in jest but I get: Invalid attempt to destructure non-iterable instance

我的代码是:

    const generator = mySaga()
    expect(generator.next().value).toEqual(all([
      call(fetchCustomers),
      call(fetchProducts)
    ]))

推荐答案

要处理错误，有必要首先了解函数生成器的一般工作原理，而与redux-saga库无关.每个yield操作都会执行中断生成器实例，并在输入/输出条目中指向yield关键字.

To deal with an error, it is necessary to understand at first how function generator generally works, irrespective of redux-saga library. Every yield operation performs interrupting generator instance, and point with yield keyword in input/output entry.

因此，yield的右值成为generator.next().value结果，并且generator.next(RESULT)成为yield关键字的左值. Redux-saga效果不会执行任何特殊的工作，只是制作特殊的动作对象( https://github.com/redux-saga/redux-saga/blob/master/src/internal/io.js )

So, right value of yield becomes generator.next().value result, and generator.next(RESULT) becomes left value of yield keyword. Redux-saga effects does not perform any special work, just makes special actions objects (https://github.com/redux-saga/redux-saga/blob/master/src/internal/io.js )

因此，要解决原始任务，只需将值传递给next()生成器函数，该函数将在const [customers, products] = yield语句中被破坏.

So, to solve original task, just pass value to next() generator function, which will be destructured in const [customers, products] = yield statement.

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